In recent years, intensive studies have been made toward the commercialization of a medication management monitoring system for monitoring a medication state at home. The outline of this system will be described below. First, an electronic circuit is printed on a package of medicines to be taken, for example, medical capsules, tablets and the like using an electroconductive ink (silver paste) to produce a package with an electronic circuit formed thereon. Thereafter, when the package is opened in case a recipient prescribed with medicine takes medicine, an electronic circuit is cut off. Opening of the package of medicine is detected by cutting off of the electronic circuit, and a signal is sent to a server of a medical institution through the internet. During system running, when the recipient forgets to take medicine, or erroneously takes medicine, the system gives the alarm to the recipient himself or herself and also gives the recipient notice by automatically sending e-mail from the server of the medical institution. Thus, an improvement in medicine noncompliance can be made.
In order to widely popularize the above-mentioned medication management monitoring system, there are many problems to solve. It is possible to exemplify, as one of problems, the production of a medicine package on which an electronic circuit is printed using an electroconductive ink. That is, there is a need to miniaturize an electronic circuit corresponding to the medicine package so as to put the above system into practical use. Therefore, there is a need to develop a non-heat curable electroconductive ink which enables satisfactory printing accuracy, printability and adhesion, and stable electroconductivity.
In recent years, attention has been focused on printing methods using an ultraviolet curable or electron beam curable ink in flexographic printing, offset printing, gravure printing and the like. These methods have the merit of being capable of reducing the drying time since a volatile organic compound is not generated, leading to enhanced productivity, and also capable of printing on a base material having low ink absorptivity, such as a plastic film.
There have been developed many electroconductive inks which can be employed in such high-speed printing method and also exhibit high electroconductivity after curing. For example, Patent Document 1 discloses, as an electroconductive ink suited for flexographic printing, rotogravure printing and the like, a composition comprising one or more oligomers of urethane acrylates, one or more acrylate carriers of diacrylate, triacrylate and the like, one or more reactive monomers of vinylethers, one or more electroconductive fillers of a flakey silver powder, and one or more photoinitiators.
Also, Patent Document 2 discloses, as an electroconductive ink suited for flexographic printing, screen printing and the like, an active energy curable electroconductive ink composition comprising an electroconductive powder, an active energy curable resin and a diluent as essential components, wherein the active energy curable resin is composed of a polyfunctional urethane acrylate.
Furthermore, Patent Document 3 discloses, as an electroconductive ink suited for flexographic printing, gravure printing, gravure offset printing and the like, an electroconductive ink comprising electroconductive fine particles (A) having an average particle size of 0.001 to 0.10 μm and an electroconductive powder (B) having an average particle size or average equivalent circle particle size of 0.5 to 10 μm, the electroconductive ink further including a flakey, scaly, tubular, spherical or foil-like electroconductive substance and a vinyl chloride/vinyl acetate/hydroxyalkyl (meth)acrylate copolymer resin.